The Heat pump reference article from the English Wikipedia on 24-Jul-2004 (provided by Fixed Reference: snapshots of Wikipedia from wikipedia.org)

Heat pump

A heat pump is a machine, which moves heat from a low level of temperature to a higher level of temperature under supply of work.

Common examples are:

• gas compression heat pumps
• phase change heat pumps
• thermoelectric heat pumps that use the Peltier effect
• geothermal exchange heat pumps

Heat pumps are realized through several physical effects, but they are classified depending on their applications (driving energy, source and sink of heat, or a heat pump which is basically a refrigeration machine). Refrigerators, air conditioners and heating systems are all common applications of heat pumps.

When comparing the performance of heat pumps, it is best to avoid the word "efficiency", as it has many different meanings. The term coefficient of performance or COP is used to describe the ratio of heat output to electrical power consumption. A typical heat pump has a COP of about three, whereas a typical electric heater has a COP of one.

The COP of a heatpump is restricted by the second law of thermodynamics.

All temperatures T in Kelvin.

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